We will continue studies on the relation of differentiation in tumor cells, such as mouse neuroblastoma and melanoma, to the state of surface glycoproteins. Recent work on new inhibitors of protein (hence glycoprotein) synthesis shows that cells can be produced that are deficient in sialic acid and are unable to regenerate sialic acid for several days, even when the inhibitor is removed. We plan to measure the capacity of these cells in differentiated and undifferentiated states, both with and without drug treatment, to decrease their content of sialic acid, to immunize against subsequent challenge with normal tumor cells. BIBLIOGRAPHIC REFERENCES: Cahn, F. and Lubin M., Ability of Formyl-Methionyl-t RNA to Initiate Globin Synthesis in the Presence of Double-stranded RNA or in the Absence of Hemin, Molecular Biology Reports 2 49-57, 1975. Silverman, D.J. and Lubin, M., Interaction of the 5'-ends of 28S RNA in Dimerization of Hamster Ribosome, Journal of Supramolecular Structure 3:67-69, 1975.